840 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY'. 



THE ARRANGEMENT OF THE AIR-CANALS IN THE STALKS 



OF.NYMPH^AS. 



By Dr. Maxwell T. Masters, F.R.S. 



{Bead before the Scientific Committee^ February 11, 1902.) 



Many years ago I had the opportunity of studying the Nymphaeas grown 

 by the late Mr. Baxter in the Botanic Garden, Oxford. I soon found 

 that the arrangement of the air-canals which traverse the leaf-stalks and 

 the flower-stalks from end to end was sufficiently constant to allow of 

 the species in the different sections being grouped according to the 

 various ways in which the canals were disposed. A communication on 

 the subject was made to the Botanical Section of the British Association 

 in 1854, and a brief abstract was published in the Report of the 

 Association for that year, Part 2, p. 102. See also Gardeners' Chroiiichj 

 1856, p. 358. 



Illustrations of the various methods of arrangement were obtained by 

 dabbing the cut ends of the stalks on to a pad of blotting-paper saturated 

 with ink, and then pressing them lightly on to paper, a plan suggested to 

 me by Mr. W. Baxter, sen. By these means an exact representation of 

 the arrangement of the larger canals can easily be obtained. The 

 smaller canals and those which encircle the larger central tubes are not 

 so characteristic, and may for the present purpose be passed over. A 

 series of such impressions made by me at the time, including nearly 

 all the species then in cultivation, may be seen among the collection 

 of drawings in the Herbarium at Kew. 



Botanists and those who have compiled monographs of the order 

 have paid little or no heed to the disposition of the canals, probably 

 because they think it less constant than it really is, or because the 

 canals are not readily visible in dried specimens, whilst living ones are not 

 always at their disposal. 



In the communication to which I have referred the species are 

 thrown into primary groups according as the arrangement of the air- 

 tubes is alike in the leaf- stalk and in the flower-stalk respectively, 

 or as the disposition of the canals is different in those organs: Subsidiary 

 groups are founded on the particular differences observable in the 

 arrangement of the tubes in each species. 



In the first group are included N. tuberosa, odorata, minor, alba, nitida, 

 and i^ygmcBa, in all of which the arrangement of the air-tubes is nearly 

 alike, if not identical, in petiole and peduncle. Further experience leads 

 me to attach less importance to this group than formerly. In both petiole 

 and peduncle are four principal canals, placed side by side and surrounded 

 by smaller ones. To these may now be added Laydeheri fulgens and 

 caroliniana. 



In the second group, the air-canals in the petioles are arranged in the 

 same manner as those in the preceding section, but in the peduncle the 

 larger canals are arranged round the centre in a radiating manner. These 



